This study deals with the genetic determinants of human and rodent glial neoplasms and other human cancers utilizing physical, chemical, cytochemical, chromosomal and electron microscopic techniques. We will continue to quantitatively analyze the number and types of satellite and other DNAs in human glial neoplasms and in normal human cells in order to see if there are specific DNA components that are amplified or decreased in the course of malignant transformation. More detailed information on the relationship of several minor human satellite DNAs to each other and to other repeating human DNA sequences will be analyzed, various subclasses of DNA will be isolated by hydroxyapetite fractionation, density gradient centrifugation using fluorescent dyes and heavy metals, and restriction enzyme cleavage of human DNA. The relationship of some of these fragments to sequences with known function such as ribosomal cistrons, and their interspersion in high molecular weight DNA will also be further explored in order to clarify their role in the structure and organization of the human genome. The relationship of these fragments to heterochromatic and euchromatic portions of the nucleus during different phases of the cell cycle, and in glial tumors where there is marked alteration in the DNA content of the nucleus, will further clarify organizational constraints of these DNAs. A series of experiments designed to elucidate the arrangement of these DNAs in-situ at the ultrastructural level utilizing experimental scanning and transmission electron microscopy in conjunction with specific marker molecules (electron dense or particulate markers conjugated to probes specific for DNA or RNA sequences) is currently being developed to further resolve our understanding of chromatin in both normal and neoplastic cells.